The change trend was influenced by several reasons such as the aquatic habitat, the ecological characteristics of fish, the community structure of digenetic trematodes and import of live fish.

这种变化趋势受种因素影响，即水环境特点、鱼类生态习性、复殖吸虫群落结构、活物运输。

Digenetic trematodes infection on fish was analyzed in the Bohai Sea horn 1983 to 1986.The results showed that the infection value in inner sea was higher than outer sea.

1983~1986年采集于渤海鱼类感染复殖吸虫进行分析，结果表明：从外海到内海鱼类感染强度呈现加重趋势。